I'll try and find those dyno printouts you want as evidence to show where you might be wrong. From an AE111 dyno day, iirc most of us like me used 2.38"/60.5mm [FGK PG] while another guy got a HKS Super Dragger off a Supra iirc which was 3.34"/85mm and you want to know the result, loud noise =/= good curve or peak output... Drove the car later confirmed it was a pig compared to mine...

FYI 4AGE 20V is a 1.6L...

Originally Posted by JDM DC2R

if bigger better just run a 4". Think you could get a extra 10kws

All the dyno paper youve supplied are from bigger displacement or worked K20 putting out 155kws atws.
Get one on a stock b16/18 and watch the power loss of a 3'' over a correct sized performance exhaust.

This...

When you're working with Force Induction, Large Capacity or Built engine, the parameters of what constitutes as the ideal sizing is far different to that of a small capacity NA engine.

For example even with NA 2L, there are very few stock engines that will benefit from 2.75" [F20C and K20A w/ 215/220PS]. These engines benefit from that because of the aggressive factory specs they have, try this on say a stock SR20DE [165PS] or a F20B [155PS?] and see the results... I can't remember their camshaft specs to show how 'mild' they are in comparison to the F20C/K20A or your examples but you get the point...

The sizing people above and on the internet usually go with are for stock to mild bolt-ons...

What alot of people do not understand is Honda engines are different to most 4cyl setups you need to look at alot of things when it comes to choosing the right exhaust for your car with its given engine size.There are so many papers written by text book tradesmen about exhaust size + header design and so on but not one of them has ever tested there idea's but yes it works on paper and in a engine simulation computer program but in the real world its a fail,the sizes I posted before are a general idea of what I have always found to work on Honda engines and in no way am I saying I am 100% correct it just comes from years of dynoing and testing and racing these Honda engines that we all own.